This is a research program project whose objective is to understand the biology of alcohol-seeking behavior (alcoholism). The research strategy is to conduct interdisciplinary (biochemical-genetic, neurochemical, neuroanatomical, neuroendocrine, and behavioral) studies in selectively-bred rat lines that exhibit high (P and HAD lines) and low (NP and LAD lines) voluntary ethanol consumption. The hypotheses to be tested are that high alcohol-seeking behavior is associated with: 1) lower threshold for the low-dose rewarding effects of ethanol, 2) higher threshold for the aversive effects of ethanol, and 3) more rapid development and longer persistence of tolerance to the highdose, aversive effects of ethanol. The proximate goals of the program project are to identify the neuronal, neurotransmitter, and neuroendocrine systems that underlie these responses to ethanol. The ultimate goal is to identify the genes responsible for the neurobiological abnormalities that lead to abnormal alcohol-seeking behavior. There are 5 research components. (A) The Animal and Molecular Genetics Component will continue the selective breeding of the P, NP, HAD and LAD lines, search for new potential biochemical (protein as well as DNA) markers of alcohol-preference, and determine whether the known and yet-to-be-discovered associations of high ethanol drinking preference are genetic by studies in animals from crosses of the lines. (B) The Behavior and Behavioral Pharmacology Component will explore-behavioral differences between P and NP rats other than those related to alcohol and in response to other drugs. (C) The Neurochemistry Component and (D) the Neuroanatomy Component will examine how P and NP rats differ in serotonin (5HT), dopamine (DA), gamma-aminobutyric acid (GABA), and glutamate (GLU) pathways and metabolism and how the metabolism of these neurotransmitters are affected by ethanol in the P and NP rats. Methods to be employed in these studies include quantitative autoradiography (receptor ligand binding and (14)C-deoxyglucose uptake), microdialysis and HPLC analysis of neurotransmitters and metabolites, in situ hybridization and quantitative immunocytochemistry. Regions of particular interest are those thought to be part of the brain reward circuitry. The Neuroendocrinology Component (E) will examine the role of endogenous vasopressin (AVP) in tolerance development and maintenance by comparing the synthesis (mRNA), content and receptor binding of AVP in P and NP rats and how alcohol affects these parameters in these lines. It will also examine how the endogenous angiotensin (AII) system influences ethanol drinking.